Android 015 - ListView Manipulation / Refresh

android.015.java

//////////////////////////////////////////////////////////////////////////////////////////////
// in der Activity
//////////////////////////////////////////////////////////////////////////////////////////////
public class WoerterListe4Activity extends AppCompatActivity {

    ListView lstVokabel;
    private Datenbankzugriff datenbankzugriff;
    private MyListAdapter myLA;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_woerter_liste4);

        init();
    }

    private void init() {

        // Wenn eine andere als die Main Activity DB zugriff braucht,
        // einfach neu anfordern!
        datenbankzugriff = new Datenbankzugriff(this);
        myLA = new MyListAdapter(this, datenbankzugriff);

        lstVokabel = findViewById(R.id.lstVokabel);
        lstVokabel.setAdapter(myLA);

        lstVokabel.setOnItemLongClickListener(new myOILCL());
    }

    private class myOILCL implements AdapterView.OnItemLongClickListener {
        @Override
        public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
            Log.v("XXXXX - onItemLongClick", String.format("position: %d,id: %d ",position,id));
            myLA.deleteItem(position);

            /* Keine bessere Lösung fürs Refreshen der ListView gefunden, als einen neuen
             * MyListAdapter anzufordern
             * Eventuell checken:
             * https://stackoverflow.com/questions/38601316/passing-database-class-object-from-main-activity-to-another-activity
             * https://stackoverflow.com/questions/2736389/how-to-pass-an-object-from-one-activity-to-another-on-android
             */
            myLA = new MyListAdapter(WoerterListe4Activity.this, datenbankzugriff);

            lstVokabel.setAdapter(myLA);

            return true;
        }
    }
}


//////////////////////////////////////////////////////////////////////////////////////////////
// in ListAdapter
//////////////////////////////////////////////////////////////////////////////////////////////

class MyListAdapter implements ListAdapter {

    private ArrayList<Wortpaar> eintraege;
    private Context             context;
    private Datenbankzugriff    datenbankzugriff;

    public MyListAdapter(Context context, Datenbankzugriff datenbankzugriff) {
        this.context = context;
        eintraege = new ArrayList<Wortpaar>();
        this.datenbankzugriff = datenbankzugriff;

        eintraegeAusDBLesen();

    }

    public void eintraegeAusDBLesen() {
        try {

            eintraege.clear();

            ArrayList<String> zeilen = new ArrayList<String>();

            zeilen = datenbankzugriff.auslesen( "SELECT ID, English, Deutsch FROM Words;");

            for (String zeile: zeilen) {
                String[] parts = zeile.split(";");
                eintraege.add(new Wortpaar(Integer.parseInt(parts[0].toString()),
                        parts[1].toString(), parts[2].toString()));
            }
        } catch (Exception ex) {
            Toast t = Toast.makeText(context, ex.getMessage() +
                    "Aus der DB zu lesen ist nicht möglich", Toast.LENGTH_LONG );
            t.show();
        }
    }


    @Override
    public boolean areAllItemsEnabled() {
        return true;
    }

    @Override
    public boolean isEnabled(int i) {
        return true;
    }

    @Override
    public void registerDataSetObserver(DataSetObserver dataSetObserver) {

    }

    @Override
    public void unregisterDataSetObserver(DataSetObserver dataSetObserver) {

    }

    @Override
    public int getCount() {
        return eintraege.size();
    }

    @Override
    public Object getItem(int i) {
            return eintraege.get(i);
    }

    @Override
    public long getItemId(int i) {
        return i;
    }

    @Override
    public boolean hasStableIds() {
        return false;
    }

    @Override
    public View getView(int i, View view, ViewGroup viewGroup) {
        LayoutInflater li = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

        View v = li.inflate(R.layout.listitem, null);

        TextView tvEng = v.findViewById(R.id.tvEng);
        TextView tvDeu = v.findViewById(R.id.tvDeu);

        Wortpaar wp = (Wortpaar) getItem(i);
        tvEng.setText(wp.eng);
        tvDeu.setText(wp.deu);

        return v;
    }

    @Override
    public int getItemViewType(int i) {
        return 0;
    }

    @Override
    public int getViewTypeCount() {
        return 1;
    }

    @Override
    public boolean isEmpty() {
        return getCount() == 0;
    }

    public void deleteItem(int positionInList) {
        int dbIdToDelete;
        dbIdToDelete = eintraege.get(positionInList).dbId;
        datenbankzugriff.ausfuehren(String.format("DELETE FROM Words where ID=%d",dbIdToDelete));
        eintraegeAusDBLesen();
    }
}